Concentration of potash ores containing sylvite



Unite CONCENTRATION OF POTASH ORES CON- TAINING SYLVITE No Drawing.Application August 19, 1955 Serial No. 529,588

2 Claims. (Cl. 209-167) This invention relates to the concentration ofpotash ores containing sylvite and especially to potash ores containingmixtures of oceanic salts and clays and of which sylvite and halite arenormal constituents. The invention has for a more particular andrepresentative application the separation and concentration of thesylvite values of sylvinite ores which in their naturally occurringstate contain small but nevertheless objectionable amounts of insolubleclay-like minerals which form slimes that interfere with theconcentration of the sylvite content of such ores by flotation and otherknown concentrating procedures. A typical example of sylvinite ores ofthis type is that found in the Carlsbad district of New Mexico.

In concentrating the potash values of such ores by flotation and similarconcentrating procedures, it is the general practice to include apreliminary desliming step for removing the objectionable slimes fromthe ore before it is mixed with the collecting agent that is added tocondition the ore for the flotation step. However, it is impractical toeffect a complete removal of the slimes by the conventional mechanicalmethods. Other methods proposed for the preliminary removal of theslimes have so far proven unduly costly in terms of the cost of thereagents, increased investment for additional plant equipment and alsoincreased operating costs.

It has come to be the common practice to effect a preliminary partialremoval of the slimes by a mechanical desliming operation and to inhibitthe adverse elfect of the residual slimes upon the collector by addingan auxiliary reagent in the course of the conditioning of the pulp forthe flotation step. Examples of such auxiliary reagents are starch anddextrin, which are most effective when added in a preliminary stage ofthe conditioning of the ore before the addition of the mineralcollector. Other auxiliary agents that have been found to be highlyeffective for controlling or inhibiting the adverse effect of the clayslimes are the polyglycols and their ethers disclosed in the copendingapplication of William Aubrey Smith, Vernon L. Mattson, Gene Meyer andRobert Baxter, Serial No. 247,384, filed September 19, 1951, now PatentNo. 2,724,499.

The present invention is based on our discovery that the use as anauxiliary agent of a member of the herein after defined group of watersoluble acrylonitrile polymers gives surprisingly good results whencompared on a quantitative basis with other reagents added for thepurpose of inhibiting or controlling the action of the slime on theamine or other conventional cationic collectingagent used in a frothflotation and in generally similar concentration treatments applied topotash ores. The

States atent O polymers that are to be used in practising the presentinvention are typified by the commercial product sold by Dow ChemicalCo. under the trade designation Separan 2610 which is understood toconsist essentially of a water soluble acrylonitrile polymer which hasundergone partial but incomplete saponification of reactive carboxylgroups. The polymers of this group may be further defined asacrylonitrile polymers in which one or more residual nitrile groups havebeen modified either by alcoholysis to produce the ester or by alkalinehydrolysis to produce a salt. They are of relatively high molecularweight.

Our investigations also show that when even extremely small additions ofthe acrylonitrile polymer are made in association with one of theseveral known auxiliary agents, e.g., one of the polyglycols or theirethers or a polymer consisting principally of mannose units such as guaror a similar mannogalactan, a distinctly high grade concentrate isproduced even when the proportion of the other auxiliary agent isreduced very substantially below the proportion required to be used whensuch other auxiliary agent is used alone.

The improvement is grade is particularly noticeable when dealing withore pulps containing considerable proportions of finer particles ofsylvite and halite and indicates that the acrylonitrile polymer promotesa greater selectivity of separation of the finer sylvite particles fromthe finer halite particles so that a smaller proportion of fine haliteparticles is carried over in the froth collected from the flotationoperation. This is a factor of very considerable importance since itfurnishes greater assurance that the concentrate will not need to bewashed to dissolve out fine halite particles carried over in the frothin order to upgrade the product. When such washing operations have to beapplied on occasion in the prior practice in order to upgrade theproduct there is of necessity a reduction in the recovery of sylvitebecause finer sylvite particles Will be dissolved along with theundesired finer halite particles.

The invention has been found particularly applicable to froth flotationprocesses but is also applicable to other concentrating operationswherein a selective mineral collector is used.

It is one of the principal objects of the invention to provide animproved method of recovering sylvite from potash ores wherein the usualcollector is employed in the flotation step and wherein theacrylonitrile polymer is added as an auxiliary reagent.

It is a further object to provide an improved flotation processemploying a mineral collector and an auxiliary reagent wherein a highyield or recovery of the valuable potash constituent is effected with aminimum amount of the auxiliary reagent.

It is a further object to provide an improved flotation processemploying a mineral collector and an auxiliary reagent wherein a highyield of the valuable potash constituents in the form of a high gradeconcentrate is effected.

Other objects and advantages of the present invention will becomeapparent as the description proceeds.

The results obtained in froth flotation tests conducted on a typicalsylvinite ore from the Carlsbad district are set out in the followingtables. In the tests represented by This I the ore was crushed and wetground to minus 8 mesh. It was thereafter screened and washed with abrine saturated with respect to the sylvite and halite constituentsuntil about 50% of the original clay slimes content of the ore wasremoved. Samples containing approximately 1000 girls. of the thuspartially deslimed ore were then conditioned at about 60% solids for oneminute with the auxiliary or slime control agents added in the form ofaqueous solutions. The amine acetate collector and the frother in theindicated proportions were then added and similarly conditioned for twominutes. by thorough mixing with the pulp. The thus conditioned and.reagentized pulp samples were then transferred to a Fagergrenlaborato-ry'flotation machine and diluted to approximately 25% solids.The flotation was then. effected at a machine speed of approximately1000 r.p.m., the froth being removed during an interval of threeminutes.

The amine collector used in all of the tests was the commercial productof Armour & Co. sold under the trade designation Arrnac TD andunderstood to consist of the water soluble acetate salts of the normalhexadecyl, octadecyl and octadecenyl amines in the approximateproportions of 30, 25 and 45 parts by weight. The frother used was acommercial grade of methyl isobutyl carbitol.

The reagent identified as X-26l0 is the commercial product sold by theDow Chemical Co. under the tradedesignation Separan 2610 hereinbeforementioned.

The reagent identified as MPG 750 was the commercialp-roduct sold underthat designation by Carbide & Carbon Chemicals Co. and is understood toconsist of methoxy polyethylene glycol polymerized to a molecular weightof approximately 750.

The reagent identified as Guar was the commercial product sold under thetrade designation Guartec by General Mills Inc. and is understood toconsist principally of mannogalactan derived from the endosperm of guarseeds. i

The reagent identified as Lytron was the commercial product sold underthe trade designation Lytron 886 by Monsanto Chemical Co. and isunderstood to be 'a calcium salt of a carboxyl-containing high molecularweight copolymer of vinyl acetate and maleic anhydride.

Table I Reagents, Lbs. per Ton Feed Analysis, Percent Percent K RecoveryTest No. of K 0 equiva- X2610 MPG Amine Frother Cone. Tail lent 750Acetate sizeof smaller than 8 mesh and a K20 equivalent about the sameas the mined ore.

The tests represented by Table II were conducted with the use of ArmacTD as the collector and methyl isobutyl arbinol as the frother, withthese reagents provided in the same proportions as in Tests Nos, 1 and2; that is, Armac TD was used in the proportion of 0.25 lb. per ton offeed and methyl isobutyl carbinol was used in the proportiQn, of 0.04lb. per tonof feed.

Table II Slime Oontrollant Analysis. Percent Percent K 0 Recovery TestNo. of K 0 equiva- Identity Lb. per Concen- Tailing lent Ton Feed trate0. 10 60. 17 17. 38. 19 0. 10 56. 72 1. 56 96. 44 0. 06 50. 89 3. 07 92.66 0.028 57. 88 9. 89 73.01 0. 10 58. 83 2. 45 93. 96 0. 25 58. 99 3. 0492. 56 0. 10 58. 49 16. 45 45. 26 0. 25 58. 02 2. 26 94. 46 0. 014 58.28 2. 51 94. 00 0.05 0.01 0. 05 0.014 0.05 0.01 0.20 0.02 0.10 0.02 0.020.01 0.05 0. 05 0.0015 18 Guar 0. 05 0.05

Tests Nos. 1-6 show that X2610 is at least several times as effective asMPG 750. When it is borne in mind that MPG 750 is several times aseffective as such prior art slime controllants as starch and dextrin itwill be understood that the results obtained with the use of X2610 aretruly remarkable.

It has also been found, as exemplified by tests Nos. 11-18 inclusive,that the addition of an exceedingly small proportion of X2610 along withone or more of several other auxiliary reagents characterized by theirability to inhibit the adverse effects of the clay slirnes brings abouta highly successful result even when the proportions of the two or moreauxiliary reagents are reduced substantially below those proportionsthat might be expected to be required if the reagents behaved merely inan additive way. In other words, the association of X2610 with one ormore of the other auxiliary reagents seems to produce a synergisticaction.

It has been further observed that the use of a partially saponifiedacrylonitrile polymer of the kind typified by X2610 in association withcertain other slime control reagents brings about desirable improvementsin the nature of the froth produced in the flotation operation. Forexample, when the acrylonitrile polymer is associated with a methoxypolyethylene glycol as the auxiliary reagent addition, the frothproduced during the flotation operation is less foamy or voluminous thanwhen the methoxy polyethylene glycol is used alone. As a result theflota-j tion action is more selective and there is a lessened tendencyfor fined particles of the halite to be picked up in the froth andcarried over in the concentrate.

It will be understood that in the above tests starvation quantities ofthe auxiliary reagents were used in many instances for the purpose ofemphasizing the contrasts in the action of the auxiliary reagents ratherthan to produce a commercial result. In other words, the results. arenot to be understood as representing the maximum recoveries and gratesobtainable with the several auxiliary re; agents and combinations ofsuch reagents involved.

Although the invention has been described with particular reference tothe results obtained when using Separan 2610 as the water solublepartially saponified acrylonitrile polymer, similar results may beobtained with the use of other members of this class.

The beneficial results realized by using, various;con-b.v binations ofwater soluble partially saponifi'ed acrylonitrile polymers of the classdefined above with OtheL slime; controllants are not confined to the useof the particulan additional auxiliary reagents used in the tests hereindescribed. Similar results may be obtained by using the definedacrylonitrile polymers in association with other members of the classesrepresented by MPG 750, Guartec and Lytron 886. For the purpose of thisinvention the class represented by MPG 750 is to be understood asincluding the various polyglycols and their ethers having a molecularweight of at least about 300. Likewise in respect of combinations of oneof the defined acrylonitrile polymers with members of the classrepresented by Guartec, it is to be understood that any polymerconsisting principally of mannose units may be substituted in place ofGuartec; that is, those naturally occurring compounds such asmannogalactan and glucomannan, or any compound in which mannose unitsare predominant. Similarly in respect of combinations of one of thedefined acrylonitrile polymers with members of the class represented byLytron 886, it is to be understood that any relatively high molecularweight vinyl acetate-maleic anhydride co-polymer may be used in thecombinations. These co-polymers are available in their purely organicform and also as their alkali metal and alkaline earth metal salts.

The invention may be practiced with similar advantage when using any ofthe various cationic collectors known to be effective in floatingsylvite and similar potash values from potash ores and is not limited inits application to the use of an amine collector. It is also to beunderstood that other frothers than methyl isobutyl carbinol may be usedin the process. Other representative examples are methyl amyl alcoholand pine oil.

The invention has been found particularly applicable to froth flotationprocesses, but is adaptable to other wet stratifying processes such asskin flotation and agglomeration tabling.

We claim:

1. The improvement in the separation of sylvite from potash orescontaining sylvite in association with minor but objectionable amountsof clay slime-forming constituents by a concentrating process employinga cationic mineral collector which comprises forming a pulp of said oreby suspending the ore in a saturated aqueous solution of the soluble oreconstituents, distributing in said ore in advance of the additionthereto of the cationic mineral collector a plurality of auxiliaryagents, one of which consists essentially of about 0.02 lb. per ton ofsaid ore of a water soluble acrylonitrile polymer in which at least onenitrile group has been modified by a process selected from the groupconsisting of alcoholysis to produce an ester and alkaline hydrolysis toproduce a salt, and another of which consists of about 0.10 lb. per tonof said ore of a member having a molecular weight of at least about 300selected from the group consisting of polyglycols and their ethers.

2. The improvement in the separation of sylvite from potash oresaccording to claim 1 wherein said member is methoxy polyethylene glycolof a molecular weight of approximately 750.

References Cited in the file of this patent UNITED STATES PATENTS2,696,912 Atwood et al. Dec. 14, 1954 2,724,489 Smith et al. Nov. 22,1955 2,740,522 Aimone et a1. Apr. 3, 1956

1. THE IMPROVEMENT IN THE SEPARATION OF SYLVITE FROM POTASH ORESCONTAINING SYLVITE IN ASSOCIATION WITH MINOR BUT OBJECTIONABLE AMOUNTSOF CLAY SLIME-FORMING CONSTITUENTS BY A CONCENTRATING PROCESS EMPLOYINGA CATIONIC MINERAL COLLECTOR WHICH COMPRISES FORMING A PULP OF SAID OREBY SUSPENDING THE ORE IN A SATURATED AQUEOUS SOLUTION OF THE SOLUBLE ORECONSTITUENTS, DISTRIBUTING IN SAID ORE IN ADVANCE OF THE ADDITIONTHERETO OF THE CATIONIC MINERAL COLLECTOR A PLURALITY OF AUXILIARYAGENTS, ONE OF WHICH CONSISTS ESSENTIALLY OF ABOUT 0.02 LB. PER TON OFSAID ORE OF A WATER SOLUBLE ACRYLONITRILE POLYMER IN WHICH AT LEAST ONENITRILE GROUP HAS BEEN MODIFIED BY A PROCESS SELECTED FROM THE GROUPCONSISTING OF ALCOHOLYSIS TO PRODUCE AN ESTER AND ALKALINE HYDROLYSIS TOPRODUCE A SALT, AND ANOTHER OF WHICH CONSISTS OF ABOUT 0.10 LB. PER TONOF SAID ORE OF A MEMBER HAVING A MOLECULAR WEIGHT OF AT LEAST ABOUT 300SELECTED FROM THE GROUP CONSISTING OF POLYGLYCOLS AND THEIR ETHER.